Pressure sending unit



April 23, 1946.

H. F. MALONE 2,399,129

PRESSURE SENDING UNIT Filed June 25, 1943 Patented Apr. 23, 1946 PRESSURE SENDING Homer F. Malone,

Chicago, Ill., asslgnor to Stewart-Warner Corporation, Chicago, 111., a

corporation of Virginia Application June 25, 1943, Serial No. 492,245

Claims. (Cl. 201-48) My invention relates to pressure sending units and more particularly to pressure sending units of the kind used to indicate the pressure in the oiling system of an internal combustion engine and for other similar purposes.

An object of my invention is to provide a new and improved pressure sending unit having less frictional resistance than the prior art sending units and wherein the eflfect of this frictional resistance on the operation of the instrument is minimized.

Another object of my invention is to provide a new and improved pressure sending unit which may be more easily and quickly calibrated than the prior art sending units.

Another object of my invention is to provide a new and improved pressure sending unit whose operation will not be aiiected by vibration such as is commonly encountered where the sending unit is used on automobile engines or the engines of other vehicles.

Another object of my invention is to provide a new and improved pressure sending unit which eliminates the movement multiplying linkage and other complications of the prior art sending units.

Another object of my invention is to provide a new and improved sending unit which may be inexpensively manufactured by conventional processes and machines and which will provide long and trouble-free service.

Other objects and advantages will become apparent a the description proceeds.

The single flgure of the drawing represents a longitudinal section through a preferred form of my invention. In the drawing, I have illustrated an embodiment of my invention which has a mounting base 2 having a threaded end 4 adapted to be screwed into an engine block or other suitable supporting structure. The base 2 is provided with a passage 6 therethrough and I4 and I6 between the ring l2 and a shoulder l8 provided by the shell 8. The upper end of a metal bellows 20 is soldered or otherwise suitably secured to the flange l4 .and the lower end of this bellows carries a spring locating cup 22 which is secured to the bellows by'a guide shaft 24. This guide shaft has an annular enlargement 26 contacting the base of the cup 22 and the lower end of this shaft extends through a suitable opening in the head of the bellows and is staked over as indicated at 28. A layer of solder 30 may be placed over the staked end 28 to prevent leakage of oil or other fluid around the lower end of the guide shaft 24 where it passes through the head of the bellows 20.

A U-shaped strap 32 is clamped between the cup 22 and the head or lower end of the bellows 20. This strap provides contact fingers 34 engaging opposite sides of a coil 36 of resistance wire. The coil 35 is mounted on and insulated from the reduced lower end of an outer sleeve 38 whose upper end is attached to the flange, It

by way of annular shoulder 40' and staked over portions 42. 'An inner or guide sleeve 44 is located in the outer sleeve 38 and serves as a guide for the shaft 24. A spring 46 is located between .the sleeves 38 and 44 and has one end resting in the cup. The other end of the spring 46 rests in the spring receiving grooves 48 formed in the upper and'pluglike end of the sleeve 44. The grooves 48 have the same pitch as the coils of the spring 46. The extreme upper end of the load spring 46 is outwardly bent, as indicated at 50, and restsin a groove 52 formed in the upper end of the outer sleeve 38.

The upper end oi. the inner sleeve 44 rests against a plug 54 which is threaded into the upper this passage is adapted to. be placed in communication with the oiling system of the internal combustion engine or other conduit containing fluid whose pressure it is desired to measure. It will be understood by those skilled in the art that my pressure sending unit incorporates a rheostat whose resistance is varied in accordance with variations in the pressure of the fluid to be measured and that this rheostat is in the circuit of an indicator mounted on the automobile dash, or in any other convenient location.

A shell 8 has its lower end attached to the base 2 and its upper end provided with threads III for receiving the corresponding threads of a ring l2 which serves to clamp the outer edges or flanges end of the outer sleeve 38. This plug 54 is provided with tool engaging portions 55 whereby the plug may be rotated relative to outer sleeve 38 to increase or decrease the tension of the load spring 46. The upper end of the inner sleeve 44 is provided with 2. her! 58 which may be engaged by a screw driver or similar tool to rotate this sleeve relative to load spring 46 and thereby increase or decrease the number of active coils of this spring. Y

The interior of the shell 8 forms a pressure .chamber in open communication with the passageway B which connects this chamber with the engine oiling system or other fluid conduit. In

order to prevent escape of fluid from the upper end of this pressure chamber, an annular sealing gasket 6|] 0! neoprene or any other suitable mate-- rial is' securely clamped between the shoulder l8 and flange H. A cover 82 is attached to the upper end of the shell 8 by a sleeve 84 having inturned ends 66 and 88. If it is desired to exclude moisture from the interior of the bellows which forms 'what may be referred to as the internal chamber, a gasket 100i neoprene or other suitable material is placed beneath the cover 62 and is held firmly compressed while the lower end 68 of the sleeve 64 is rolled over to secure the cover to the upper end of the shell 8.

The upper end of the resistance coil 36 is attached to a copper band" which surrounds but is insulated from the inner sleeve 38. A wire H has its lower end attached to this band in any suitable manner. The main body of the wire 14 is provided with an insulating covering and the bare upper end of this wire passes through an opening 16 provided in a terminal 18 and is soldered to this terminal at the upper end of the opening. The terminal 18 is mounted on but insulated from the cover 62 by means of insulating rings 80, 82 and 84. The rings 80 and 84 are preferably formed of Bakelite or similar relatively strong, rigid material, whereas the rings 82 are preferably of neoprene or similar rubberlike material.

In the manufacture of my new and improved pressure sending unit, the unit is calibrated before the cover 62 is attached to the shell 3 and before the wire 14 is inserted in and soldered to the terminal 18. When all of the parts except the cover have been initially assembled, the plug 54 only engages the end threads of the outer sleeve 38 and with no pressure in the pressure chamber the contacts 34 normally rest high up on the rheostat coil 36.

Plug 54 is screwed in until the contacts 34 are moved down to the proper starting position which may correspond to a value of 100 ohms resistance for the rheostat. When the contacts reach this starting or zero pressure position, further screwing in of the plug 54 is discontinued and pressure is applied to the pressure chamber through passageway 6 in base 2, In calibrating, it is usual to build up the fluid pressure to the maximum pressure, for example 80 pounds per square inch, at which the rheostat resistance should be a minimum, for example, one ohm. If the rheostat reaches its minimum resistance at a pressure lower than the maximum, for example, '75 pounds per square inch, the load spring 45 is offering insuflicient opposition to movement of the bellows.

This can be corrected by decreasing the number of active coils of the load spring and is accomplished by applying a screwdriver to the kerf 58 and rotating inner sleeve 44 an appropriate amount, such for example, as a complete turn which will have the effect of eliminating one coil of the load spring. The zero position of the contacts 34 is then re-set by rotating plug 54. Pressure is again applied to test the setting of the rheostat for maximum pressure and if the calibration is still incorrect, further adjustments are made until the calibration is correct for both maximum and zero loads.

As soon as correct calibration is attained, plug 54 and inner sleeve 44 are looked in adjusted position by drops of solder, or in any other suitable manner, so that these parts can not shift out of proper adjustment. The bare upper end of wire 14 is then inserted in opening 16 in terminal 18 and cover 62 is secured in place. When first inserted in opening 16, the bare upper end of the wire 14 is several inches longer than shown in the drawing and as soon as the cover is securely in place, the wire is soldered in the upper end of opening 16, as indicated at 88, and the projecting end is then cut off. The unit is now complete.

I wish to call particular attention to the fact that movement of the bellows results in corresponding movement of the contacts over the rheostat coil, as no linkages are interposed between the contacts and the free end of the bellows. The frictional resistance of the usual linkages is, therefore, avoided so that frictional resistance to movement of the parts is reduced to a minimum. The bellows may be made of relatively large cross-section, affording a maximumarea exposed to fluid pressure so that the force required to overcome frictional resistance is a very small part of the total force available to move the free end of the bellows. Under these circumstances, the frictional engagement between the contacts and the resistance coil can be made sufficient to afford proper electrical contacts therebetween, regardless of any vibrations to which the unit is subjected, and this slight frictional resistance between the contacts and resistance coil will have no appreciable effect on the sensitivity of the instrument.

Another feature of my invention lies in the means for protecting the unit against excessive pressure. I preferably make the parts of such dimensions that when the instrument is subjected to maximum pressure, the upper end of cup 22 is closely adjacent the lower end of outer sleeve 38. At the same time the contacts 34 engage resistance coil 36 adjacent the upper end thereof. Any pressure sufficient to move the contacts beyond the upper end of the resistance coil 36 will bring the upper end of cup 22 in engagement with the lower end of sleeve 38. Thereafter any excess pressure will be borne by sleeve 38 and cup 22 and the remaining parts of the unit will be relieved of the necessity of resisting such excessive pressures.

It should be noted that the several parts of my novel pressure sending unit are of simple and rugged construction and may be readily made of conventional materials and with conventional manufacturing methods and equipment. This unit may be easily assembled and calibrated and quickly installed in the lubricating system of an internal combustion engine or in any other location where it may be utilized to measure fluid pressure in a conduit or condenser.

While I have illustrated and described only a single embodiment of my invention, it is to be understood that my invention is not limited to the details shown and described but may assume numerous other forms and that my invention includes all modifications and variations falling within the appended claims.

I claim:

1. A. pressure sending unit of the class described, comprising a tubular base, a shell mounted on said base, a bellows mounted in said shell, a stationary sleeve located in one end of said bellows, a resistance wire wound about said sleeve, a spring in said sleeve for expanding said bellows, said bellows being contracted by fluid pressure in said shell, a spring receiving cup carried by said bellows, said cup cooperating with said sleeve to limit movement of said bellows under the force of fluid pressure, and a contact carried by said bellows and directly movable over said resistance.

2. A pressure sending unit of the class described, comprising means providing a pressure chamber, a bellows located in said chamber, a spring for expanding said bellows, said bellows being contracted by fluid pressure in said chamber, a sleeve in said bellows forming a support for said spring, means for rotating said sleeve to vary the efi'ective length of said spring, and means for moving said sleeve longitudinally of said bellows to adjust the tension of said spring.

3. A pressure sending unit of the class de scribed, comprising means providing a pressure chamber, a spring for expanding said bellows, said bellows being contracted by fluid pressure in said chamber; a support for said spring, means for rotating said support to vary the length of said spring, and means for moving said support lengthwise of said bellows to adjust the tension of said spring.

4. A pressure sending unit of the class described, comprising means providing a pressure chamber, a bellows located in said chamber, a pair of sleeves in one end of said bellows, a bellows expanding spring between said sleeves, a guide shaft for said bellows slidably engaging one 01 said sleeves, and a rheostat variable in response to movements of said bellows.

5. A pressure sending unit oi! the class described, comprising a base, a shell mounted on said base, said shell having a shoulder adjacent an end thereof remote from said base, a ring threaded into the last-named end of said shell, a pair of flanges clamped between said ring and said shoulder, a bellows having an open end attached to one of said flanges, a stationary sleeve attached to the other of said flanges and located in said bellows, a resistance wire carried by said sleeve, and a contact attached directly to said bellows and movable over said resistance wire.

6. A pressure sending unit of the class described, comprising a base, a shell mounted on said base, said shell having a shoulder adjacent an end thereof remote from said base, a ring threaded into the last-named end of said shell, a pair of flanges. clamped between said ring and said shoulder, a bellows having an open end attached to one of said flanges, a stationary sleeve attached to the other 01 said flanges and located in said bellows, a resistance wire carried by said sleeve, a contact attached directly to said bellows and movable over said resistance wire, a

scribed, comprising a base, a shell mounted on said base, said shell having a shoulder adjacent an end thereof remote from said base, a ring threaded into the last-named end 01 said shell. a pair fianges clamped between said ring and said shoulder. a bellows having an open end said sleeves and tending to expand said bellows,

and a spring receiving cup attached to said bellows, said cup engageable with one of said sleeves to limit movement of said bellows in one direction.

8. A pressure sending unit of the class described, comprising a base, a shell mounted on said base, said shell having a shoulder adjacent an end thereof remote from said base, a ring threaded into the last-named end of said shell, a pair of flanges clamped between said ring and said shoulder, a bellows having an open end attached to one of said flanges, a stationary sleeve attached to the other of said flanges and located in said bellows, a resistance wire carried by said sleeve, a contact attached directly to said bellows and movable over said resistance wire, a second sleeve located in and threadedly engaging said first-mentioned sleeve, a spring confined between said sleeves and tending to expand said bellows, a spring receiving cup attached to said bellows, said cup engageable with one of said sleeves to limit movement of said bellows in one direction, and a guide member slidable in one of said sleeves and securing said cup and contact to said bellows.

9. A pressure sending unit of the class described, comprising means providing a pressure chamber, a bellows located in said chamber and contracted by fluid pressure therein, a spring for expanding said bellows, a first sleeve locatedin one end of said bellows and having a slot receiving one end of said spring to prevent rotation thereof and a second sleeve rotatably mounted in said first sleeve adjustable to vary the adjusted length of said spring.

10. A pressure sending unit of the class described, comprising means providing a pressure chamber, a bellows located in said chamber and contracted by fluid pressure therein, a spring for expanding said bellows, a first sleeve located in one end 01 said bellows and having a slot receiving one end oi! said spring to prevent rotation thereof, a second sleeve rotatably mounted in said flrst sleeve addustable to vary the adjusted length ofv said spring, and a plug threadedly engaging said first sleeve and adjustable to move HOMER r'. MALONE. 

